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Manuál Linux
[Linux manuál]

exit: způsobit normální ukončení programu

Originální popis anglicky: exit - cause normal program termination

Návod, kniha: Linux Programmer's Manual


#include <stdlib.h>
void exit(int status);


The exit() function causes normal program termination and the the value of status & 0377 is returned to the parent (see wait(2)). All functions registered with atexit() and on_exit() are called in the reverse order of their registration, and all open streams are flushed and closed. Files created by tmpfile() are removed.
The C standard specifies two defines EXIT_SUCCESS and EXIT_FAILURE that may be passed to exit() to indicate successful or unsuccessful termination, respectively.


The exit() function does not return.


SVID 3, POSIX, BSD 4.3, ISO 9899 (``ANSI C'')


During the exit processing, it is possible to register additional functions with atexit() and on_exit(). Always the last-registered function is removed from the chain of registered functions, and invoked. It is undefined what happens if during this processing either exit() or longjmp() is called.
The use of EXIT_SUCCESS and EXIT_FAILURE is slightly more portable (to non-Unix environments) than that of 0 and some nonzero value like 1 or -1. In particular, VMS uses a different convention.
BSD has attempted to standardize exit codes - see the file <sysexits.h>.
After exit(), the exit status must be transmitted to the parent process. There are three cases. If the parent has set SA_NOCLDWAIT, or has set the SIGCHLD handler to SIG_IGN, the status is discarded. If the parent was waiting on the child it is notified of the exit status. In both cases the exiting process dies immediately. If the parent has not indicated that it is not interested in the exit status, but is not waiting, the exiting process turns into a "zombie" process (which is nothing but a container for the single byte representing the exit status) so that the parent can learn the exit status when it later calls one of the wait() functions.
If the implementation supports the SIGCHLD signal, this signal is sent to the parent. If the parent has set SA_NOCLDWAIT, it is undefined whether a SIGCHLD signal is sent.
If the process is a session leader and its controlling terminal the controlling terminal of the session, then each process in the foreground process group of this controlling terminal is sent a SIGHUP signal, and the terminal is disassociated from this session, allowing it to be acquired by a new controlling process.
If the exit of the process causes a process group to become orphaned, and if any member of the newly-orphaned process group is stopped, then a SIGHUP signal followed by a SIGCONT signal will be sent to each process in this process group.


_exit(2), wait(2), atexit(3), on_exit(3), tmpfile(3)
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